U.S. patent application number 12/772178 was filed with the patent office on 2011-11-03 for compensation orthodontic archwire design.
Invention is credited to Phillip Getto, Rohit Sachdeva, Peer Sporbert.
Application Number | 20110270583 12/772178 |
Document ID | / |
Family ID | 44858979 |
Filed Date | 2011-11-03 |
United States Patent
Application |
20110270583 |
Kind Code |
A1 |
Getto; Phillip ; et
al. |
November 3, 2011 |
COMPENSATION ORTHODONTIC ARCHWIRE DESIGN
Abstract
Method and workstation automatically designing an arch-wire
including compensations for auxiliary appliances or biological
constraints exerting unknown forces to achieve a pre-planned
treatment goal are disclosed. The adjusted customized arch-wire is
designed after an initial customized arch-wire has been used to
treat a patient and is at or near equilibrium. The initial custom
arch-wire is first designed by producing a 3D computer-based,
geometrical model of a patient's dentition, locating brackets on
the digital tooth model, moving the digital tooth models to planned
final positions and orientations, and then calculating a wire which
fits in the slots of the brackets while the teeth are in their
planned final positions and exerts no forces on the brackets. After
a period of time the teeth will move under the force of the wire
and will eventually move into positions such that the forces from
all appliances and biological systems are in equilibrium. If the
teeth are not in the final planned positions at that point in time,
the adjusted custom arch-wire is designed and applied.
Inventors: |
Getto; Phillip; (Plano,
TX) ; Sachdeva; Rohit; (Plano, TX) ; Sporbert;
Peer; (Berlin, DE) |
Family ID: |
44858979 |
Appl. No.: |
12/772178 |
Filed: |
May 1, 2010 |
Current U.S.
Class: |
703/1 |
Current CPC
Class: |
A61C 7/20 20130101; A61C
7/002 20130101 |
Class at
Publication: |
703/1 |
International
Class: |
G06F 17/50 20060101
G06F017/50 |
Claims
1. A method of designing the shape of a compensating orthodontic
arch-wire inserted into slots of brackets bonded to teeth of an
orthodontic patient based upon monitoring of treatment and initial
archwire design, utilizing a workstation, comprising the steps of:
a. retrieving a three-dimensional digital model of target positions
of teeth of an orthodontic patient; b. retrieving initial design of
archwire customized to move patient's teeth from malocclusion to
target set-up; c. obtaining a three-dimensional digital model of
current positions of teeth of said orthodontic patient; d.
computing differences in 3 translational degrees of freedom and 3
rotational degrees of freedom between said target positions of
teeth and said current positions of teeth; and e. designing shape
of compensating orthodontic arch-wire based upon adding said
differences to initial archwire design.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is related to application Docket No.
ORA-10-001, filed Apr. 30, 2010, Title: BRACKET-SLOT-TO-WIRE PLAY
COMPENSATION ARCHWIRE DESIGN, and application Ser. No. 10/428,461,
filed May 2, 2003, pending, which is a continuation-in-part of
application Ser. No. 09/834,412, filed Apr. 13, 2001, now issued as
U.S. Pat. No. 6,632,089, the entire contents of which are
incorporated by reference herein. This application is also related
to patent application Ser. No. 10/429,123, filed May 2, 2003, now
issued as U.S. Pat. No. 7,234,937, the entire contents of which are
incorporated by reference herein. This application is also related
to application Ser. No. 09/835,039, filed Apr. 13, 2001, now issued
as U.S. Pat. No. 6,648,640, the entire contents of which are
incorporated by reference herein.
BACKGROUND OF THE INVENTION
[0002] A. Field of the Invention
[0003] This invention relates generally to the field of
orthodontics. More particularly, the invention relates to designing
an adjusted customized arch-wire after an initial customized
arch-wire has been used to treat a patient and is at or near
equilibrium but the patient's teeth have not reached the target
position. The adjusted customized archwire is designed by
compensating the initial design based upon the tooth displacement
for one or more teeth required in the progress model.
[0004] B. Description of Related Art
[0005] In orthodontics, a patient suffering from a malocclusion is
typically treated by bonding brackets to the surface of the
patient's teeth. The brackets have slots for receiving an archwire.
The bracket-archwire interaction governs forces applied to the
teeth and defines the desired direction of tooth movement.
Typically, the bends in the wire are made manually by the
orthodontist. During the course of treatment, the movement of the
teeth is monitored. Corrections to the bracket position and/or wire
shape are made manually by the orthodontist.
[0006] The key to efficiency in treatment and maximum quality in
results is a realistic simulation of the treatment process. Today's
orthodontists have the possibility of taking plaster models of the
upper and lower jaw, cutting the model into single tooth models and
sticking these tooth models into a wax bed, lining them up in the
desired position, the so-called set-up. This approach allows for
reaching a perfect occlusion without any guessing. The next step is
to bond a bracket at every tooth model. This would tell the
orthodontist the geometry of the wire to run through the bracket
slots to receive exactly this result. The next step involves the
transfer of the bracket position to the original malocclusion
model. To make sure that the brackets will be bonded at exactly
this position at the real patient's teeth, small templates for
every tooth would have to be fabricated that fit over the bracket
and a relevant part of the tooth and allow for reliable placement
of the bracket on the patient's teeth. To increase efficiency of
the bonding process, another option would be to place each single
bracket onto a model of the malocclusion and then fabricate one
single transfer tray per jaw that covers all brackets and relevant
portions of every tooth. Using such a transfer tray guarantees a
very quick and yet precise bonding using indirect bonding.
[0007] However, it is obvious that such an approach requires an
extreme amount of time and labor and thus is too costly, and this
is the reason why it is not practiced widely. The normal
orthodontist does not fabricate set-ups; he places the brackets
directly on the patient's teeth to the best of his knowledge, uses
an off-the-shelf wire and hopes for the best. There is no way to
confirm whether the brackets are placed correctly; and misplacement
of the bracket will change the direction and/or magnitude of the
forces imparted on the teeth. While at the beginning of treatment
things generally run well as all teeth start to move at least into
the right direction, at the end of treatment a lot of time is lost
by adaptations and corrections required due to the fact that the
end result has not been properly planned at any point of time. For
the orthodontist this is still preferable over the lab process
described above, as the efforts for the lab process would still
exceed the efforts that he has to put in during treatment. And the
patient has no choice and does not know that treatment time could
be significantly reduced if proper planning was done.
[0008] U.S. Pat. No. 5,431,562 to Andreiko et al. describes a
computerized, appliance-driven approach to orthodontics. In this
method, first certain shape information of teeth is acquired. A
uniplanar target archform is calculated from the shape information.
The shape of customized bracket slots, the bracket base, and the
shape of an orthodontic archwire, are calculated in accordance with
a mathematically-derived target archform. The goal of the Andreiko
et al. method is to give more predictability, standardization, and
certainty to orthodontics by replacing the human element in
orthodontic appliance design with a deterministic, mathematical
computation of a target archform and appliance design. Hence the
'562 patent teaches away from an interactive, computer-based system
in which the orthodontist remains fully involved in patient
diagnosis, appliance design, and treatment planning and
monitoring.
[0009] More recently, in the late 1990's Align Technologies began
offering transparent, removable aligning devices as a new treatment
modality in orthodontics. In this system, a plaster model of the
dentition of the patent is obtained by the orthodontist and shipped
to a remote appliance manufacturing center, where it is scanned
with a laser. A computer model of the dentition in a target
situation is generated at the appliance manufacturing center and
made available for viewing to the orthodontist over the Internet.
The orthodontist indicates changes they wish to make to individual
tooth positions. Later, another virtual model is provided over the
Internet and the orthodontist reviews the revised model, and
indicates any further changes. After several such iterations, the
target situation is agreed upon. A series of removable aligning
devices or shells are manufactured and delivered to the
orthodontist. The shells, in theory, will move the patient's teeth
to the desired or target position.
[0010] U.S. Pat. No. 6,632,089 to Rubbert discloses an interactive,
software-based treatment planning method to correct a malocclusion.
The method can be performed on an orthodontic workstation in a
clinic or at a remote location such as a lab or precision appliance
manufacturing center. The workstation stores a virtual
three-dimensional model of the dentition of a patient and patient
records. The virtual model is manipulated by the user to define a
target situation for the patient, including a target archform and
individual tooth positions in the archform. Parameters for an
orthodontic appliance, such as the location of orthodontic brackets
and resulting shape of a customized orthodontic archwire, are
obtained from the simulation of tooth movement to the target
situation and the placement position of virtual brackets. However,
often, the effectiveness of a customized archwire reaches an
equilibrium at some point in time where the archwire ceases to
exert force on the teeth even though the teeth have not yet
attained the desired target position. Therefore a need exists to
for adjusting the design of a customized archwire by compensating
the initial design based upon tooth displacements called for in the
progress model of the patient with respect to the target model
where the teeth should ultimately reach indicating the end of the
treatment. The present invention meets this need.
SUMMARY OF THE INVENTION
[0011] Often, the initially designed customized archwire for moving
a patient's teeth from malocclusion to the desired target set-up
reaches an equilibrium without achieving the planned treatment
goal. In such a case the current or progress model of the patient's
teeth shows tooth displacements required to achieve the target
positions. The preferred embodiment of the invention disclosed
herein enables the practitioner evaluate the progress model in
order to determine the tooth displacements still required to move
the teeth in the desired positions; and design the compensation
archwire by making adjustments necessary to the initial design of
the arch wire. The compensations can be made to achieve
displacements in all 6 degrees of freedom, i.e. misial or distal
translational displacement, buccal or lingual translational
displacement; occlusal or gingival translational displacement,
facial or lingual torque, mesial or distal angulation and mesial or
distal rotation. The treatment planning software performs
calculations automatically to determine the extent and the nature
of displacements required from the three dimensional digital models
of progress and the target. The practitioner can look at the
displacements and if they are satisfactory, then instructs the
workstation to perform the compensation design of the archwire
automatically. The workstation provides the tools whereby the
practitioner can override one or more displacements that were
automatically calculated by the treatment planning workstation; and
specify new values for the selected displacements. Then the
compensation archwire design is performed using the displacement
parameters specified by the practitioner or the treatment
planner.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Presently preferred embodiments of the invention are
described below in reference to the appended drawings, wherein like
reference numerals refer to like elements in the various views, and
in which:
[0013] FIG. 1 is block diagram of a system for creating a
three-dimensional virtual patient model and for diagnosis and
planning treatment of the patient.
[0014] FIG. 2A shows the front-view of an example bracket and an
example archwire sliding segment inserted in the slot of the
bracket.
[0015] FIG. 2B shows a cross-sectional view of the bracket and the
archwire sliding segment shown in FIG. 2A.
[0016] FIG. 3 is similar to FIG. 2B and shows the cross-section of
the bracket and the archwire shown in FIG. 2A with the archwire
rotated to apply torque.
[0017] FIG. 4A shows an example bracket-slot with industry standard
specification of width; and an example archwire with industry
standard specification. The archwire has rectangular cross-section
with sharp un-rounded edges.
[0018] FIG. 4B shows an example bracket-slot and an example
archwire with industry standard specifications the same as in FIG.
4A; however, the archwire in FIG. 4B has rectangular cross-section
with rounded edges.
[0019] FIG. 5 shows an example where a tooth requires facial
torque, which has been automatically calculated by the treatment
planning software. FIG. 5 also shows the slot for the bracket
associated with the tooth and the archwire cross-section rotated to
deliver the desired facial torque.
[0020] FIG. 6 shows the same example tooth as in FIG. 5. However,
the practitioner overrides the automatic determination by the
treatment planning software and changes the torque to a lingual
torque. FIG. 6 shows the same slot for the bracket as in FIG. 5
associated with the tooth. However, the archwire cross-section is
now rotated in the lingual direction to deliver the desired lingual
torque.
[0021] FIG. 7 shows the same example tooth as in FIG. 5. The tooth
is shown in two different positions, namely the tooth in the target
position superimposed over the tooth in the initial position, in
FIG. 7. Also shown are the bracket and the archwire cross-section
rotated to deliver facial torque.
[0022] FIG. 8A shows that a tooth requires a mesial angulation. The
straight archwire segment is rotated around the y-axis in the
mesial direction such that the straight archwire segment makes
surface contact with the walls of the bracket slot at two
locations. This type and amount of offset would provide the desired
degree of mesial angulation.
[0023] FIG. 8B is similar to FIG. 8A with the exception that FIG.
8B shows that a tooth requires a distal angulation. In this case,
the straight archwire segment is rotated around the y-axis in the
distal direction such that the straight archwire segment makes
surface contact with the walls of the bracket slot at two
locations. This type and amount of offset would provide the desired
degree of distal angulation.
[0024] FIG. 9 illustrates the process of designing the desired
offset to compensate for the bracket-slot-to-wire play by way of an
example.
[0025] FIG. 10 shows an example digital or virtual target setup
model of a patient's dentition.
[0026] FIG. 11 shows the three-dimensional digital or virtual
progress model of the current state of the dentition of the same
patient as in FIG. 10. The figure also lists the nature and amount
of displacement still required for each tooth relative to the
target setup.
[0027] FIG. 12 shows the virtual progress model with the brackets
attached to the teeth.
[0028] FIG. 13 shows a superimposed virtual model of the patient's
dentition obtained by combining the target set-up model of FIG. 10
with the progress model of FIG. 11.
[0029] FIG. 13A shows `Create Compensation Wire` tab on the
treatment planning workstation display.
[0030] FIG. 14 shows the virtual target set-up model of the
patient's dentition previously shown in FIG. 10; and the shape of
the newly designed archwire in order to compensate for deviations
between the target setup and the progress model. Also shown in FIG.
14 is the virtual model showing teeth, brackets and the
compensation archwire.
[0031] FIG. 15 shows the virtual superimposed model the same as in
FIG. 13 along with the newly designed compensation archwire.
[0032] FIG. 16A shows the comparison between the set-up archwire
and the newly designed compensation archwire both shown in the arch
form.
[0033] FIG. 16B shows the same two wires as in FIG. 16A, but from
the archwire plane view perspective.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENT
[0034] Before describing the features of this invention in detail,
an overview of a unified workstation will be set forth initially.
The workstation provides software features that create two
dimensional and/or three-dimensional virtual patient model on a
computer, which can be used for purposes of treatment planning in
accordance with a presently preferred embodiment.
[0035] Many of the details and computer user interface tools which
a practitioner may use in adjusting tooth position, designing
appliance shape and location, managing space between teeth, and
arriving at a finish tooth position using interaction with a
computer storing and displaying a virtual model of teeth are set
forth in the prior application Ser. No. 09/834,412 filed Apr. 13,
2001, and in published OraMetrix patent application WO 01/80761,
the contents of which are incorporated by reference herein. Other
suites of tools and functions are possible and within the scope of
the invention. Such details will therefore be omitted from the
present discussion.
GENERAL DESCRIPTION
[0036] A unified workstation environment and computer system for
diagnosis, treatment planning and delivery of therapeutics,
especially adapted for treatment of craniofacial structures, is
described below. In one possible example, the system is
particularly useful in diagnosis and planning treatment of an
orthodontic patient. Persons skilled in the art will understand
that the invention, in its broader aspects, is applicable to other
craniofacial disorders or conditions requiring surgery,
prosthodontic treatment, restorative treatment, etc.
[0037] A presently preferred embodiment is depicted in FIG. 1. The
overall system 100 includes a general-purpose computer system 10
having a processor (CPU 12) and a user interface 14, including
screen display 16, mouse 18 and keyboard 20. The system is useful
for planning treatment for a patient 34.
[0038] The system 100 includes a computer storage medium or memory
22 accessible to the general-purpose computer system 10. The memory
22, such as a hard disk memory or attached peripheral devices,
stores two or more sets of digital data representing patient
craniofacial image information. These sets include at least a first
set of digital data 24 representing patient craniofacial image
information obtained from a first imaging device and a second set
of digital data 26 representing patient craniofacial image
information obtained from a second image device different from the
first image device. The first and second sets of data represent, at
least in part, common craniofacial anatomical structures of the
patient. At least one of the first and second sets of digital data
normally would include data representing the external visual
appearance or surface configuration of the face of the patient.
[0039] In a representative and non-limiting example of the data
sets, the first data set 24 could be a set of two dimensional color
photographs of the face and head of the patient obtained via a
color digital camera 28, and the second data set is
three-dimensional image information of the patient's teeth,
acquired via a suitable scanner 30, such as a hand-held optical 3D
scanner, or other type of scanner. The memory 22 may also store
other sets 27 of digital image data, including digitized X-rays,
MRI or ultrasound images, CT scanner etc., from other imaging
devices 36. The other imaging devices need not be located at the
location or site of the workstation system 100. Rather, the imaging
of the patient 34 with one or other imaging devices 36 could be
performed in a remotely located clinic or hospital, in which case
the image data is obtained by the workstation 100 over the Internet
37 or some other communications medium, and stored in the memory
22.
[0040] The system 100 further includes a set of computer
instructions stored on a machine-readable storage medium. The
instructions may be stored in the memory 22 accessible to the
general-purpose computer system 10. The machine-readable medium
storing the instructions may alternatively be a hard disk memory 32
for the computer system 10, external memory devices, or may be
resident on a file server on a network connected to the computer
system, the details of which are not important. The set of
instructions, described in more detail below, comprise instructions
for causing the general computer system 10 to perform several
functions related to the generation and use of the virtual patient
model in diagnostics, therapeutics and treatment planning.
[0041] These functions include a function of automatically, and/or
with the aid of operator interaction via the user interface 14,
superimposing the first set 24 of digital data and the second set
26 of digital data so as to provide a composite, combined digital
representation of the craniofacial anatomical structures in a
common coordinate system. This composite, combined digital
representation is referred to herein occasionally as the "virtual
patient model," shown on the display 16 of FIG. 1 as a digital
model of the patient 34. Preferably, one of the sets 24, 26 of data
includes photographic image data of the patient's face, teeth and
head, obtained with the color digital camera 28. The other set of
data could be intra-oral 3D scan data obtained from the hand-held
scanner 30, CT scan data, X-Ray data, MRI, etc. In the example of
FIG. 1, the hand-held scanner 30 acquires a series of images
containing 3D information and this information is used to generate
a 3D model in the scanning node 31, in accordance with the
teachings of the published PCT application of OraMetrix, PCT
publication no. WO 01/80761, the content of which is incorporated
by reference herein. Additional data sets are possible, and may be
preferred in most embodiments. For example the virtual patient
model could be created by a superposition of the following data
sets: intra-oral scan of the patient's teeth, gums, and associated
tissues, X-Ray, CT scan, intra-oral color photographs of the teeth
to add true color (texture) to the 3D teeth models, and color
photographs of the face, that are combined in the computer to form
a 3D morphable face model. These data sets are superimposed with
each other, with appropriate scaling as necessary to place them in
registry with each other and at the same scale. The resulting
representation can be stored as a 3D point cloud representing not
only the surface on the patient but also interior structures, such
as tooth roots, bone, and other structures. In one possible
embodiment, the hand-held in-vivo scanning device is used which
also incorporates a color CCD camera to capture either individual
images or video.
[0042] The software instructions further includes a set of
functions or routines that cause the user interface 16 to display
the composite, combined digital three-dimensional representation of
craniofacial anatomical structures to a user of the system. In a
representative embodiment, computer-aided design (CAD)-type
software tools are used to display the model to the user and
provide the user with tools for viewing and studying the model.
Preferably, the model is cable of being viewed in any orientation.
Tools are provided for showing slices or sections through the model
at arbitrary, user defined planes. Alternatively, the composite
digital representation may be printed out on a printer or otherwise
provided to the user in a visual form.
[0043] The software instructions further include instructions that,
when executed, provide the user with tools on the user interface 14
for visually studying, on the user interface, the interaction of
the craniofacial anatomical structures and their relationship to
the external, visual appearance of the patient. For example, the
tools include tools for simulating changes in the anatomical
position or shape of the craniofacial anatomical structures, e.g.,
teeth, jaw, bone or soft tissue structure, and their effect on the
external, visual appearance of the patient. The preferred aspects
of the software tools include tools for manipulating various
parameters such as the age of the patient; the position,
orientation, color and texture of the teeth; reflectivity and
ambient conditions of light and its effect on visual appearance.
The elements of the craniofacial and dental complex can be analyzed
quickly in either static format (i.e., no movement of the
anatomical structures relative to each other) or in an dynamic
format (i.e., during movement of anatomical structures relative to
each other, such as chewing, occlusion, growth, etc.). To
facilitate such modeling and simulations, teeth may be modeled as
independent, individually moveable 3 dimensional virtual objects,
using the techniques described in the above-referenced OraMetrix
published PCT application, WO 01/80761.
[0044] The workstation environment provided by this invention
provides a powerful system and for purposes of diagnosis, treatment
planning and delivery of therapeutics. For example, the effect of
jaw and skull movement on the patient's face and smile can be
studied. Similarly, the model can be manipulated to arrive at the
patient's desired feature and smile. From this model, and more
particularly, from the location and position of individual
anatomical structures (e.g., individual tooth positions and
orientation, shape of arch and position of upper and lower arches
relative to each other), it is possible to automatically back solve
for or derive the jaw, tooth, bone and/or soft tissue corrections
that must be applied to the patient's initial, pre-treatment
position to provide the desired result. This leads directly to a
patient treatment plan.
[0045] These simulation tools, in a preferred embodiment, comprise
user-friendly and intuitive icons 35 that are activated by a mouse
or keyboard on the user interface of the computer system 10. When
these icons are activated, the software instruction provide pop-up,
menu, or other types screens that enable a user to navigate through
particular tasks to highlight and select individual anatomical
features, change their positions relative to other structures, and
simulate movement of the jaws (chewing or occlusion). Examples of
the types of navigational tools, icons and treatment planning tools
for a computer user interface that may be useful in this process
and provide a point of departure for further types of displays
useful in this invention are described in the patent application of
Rudger Rubbert et al., Ser. No. 09/835,039 filed Apr. 13, 2001, the
contents of which are incorporated by reference herein.
[0046] The virtual patient model, or some portion thereof, such as
data describing a three-dimensional model of the teeth in initial
and target or treatment positions, is useful information for
generating customized orthodontic appliances for treatment of the
patient. The position of the teeth in the initial and desired
positions can be used to generate a set of customized brackets, and
customized flat planar archwire, and customized bracket placement
jigs, as described in the above-referenced Andreiko et al. patents.
Alternatively, the initial and final tooth positions can be used to
derive data sets representing intermediate tooth positions, which
are used to fabricate transparent aligning shells for moving teeth
to the final position, as described in the above-referenced Chisti
et al. patents. The data can also be used to place brackets and
design a customized archwire as described in the previously cited
application Ser. No. 09/835,039.
[0047] To facilitate sharing of the virtual patient model among
specialists and device manufacturers, the system 100 includes
software routines and appropriate hardware devices for transmitting
the virtual patient model or some subset thereof over a computer
network. The system's software instructions are preferably
integrated with a patient management program having a scheduling
feature for scheduling appointments for the patient. The patient
management program provides a flexible scheduling of patient
appointments based on progress of treatment of the craniofacial
anatomical structures. The progress of treatment can be quantified.
The progress of treatment can be monitored by periodically
obtaining updated three-dimensional information regarding the
progress of treatment of the craniofacial features of the patient,
such as by obtaining updated scans of the patient and comparison of
the resulting 3D model with the original 3D model of the patient
prior to initiation of treatment.
[0048] Thus, it is contemplated that system described herein
provides a set of tools and data acquisition and processing
subsystems that together provides a flexible, open platform or
portal to a variety of possible therapies and treatment modalities,
depending on the preference of the patient and the practitioner.
For example, a practitioner viewing the model and using the
treatment planning tools may determine that a patient may benefit
from a combination of customized orthodontic brackets and wires and
removable aligning devices. Data from the virtual patient models is
provided to diverse manufacturers for coordinated preparation of
customized appliances. Moreover, the virtual patient model and
powerful tools described herein provide a means by which the
complete picture of the patient can be shared with other
specialists (e.g., dentists, maxilla-facial or oral surgeons,
cosmetic surgeons, other orthodontists) greatly enhancing the
ability of diverse specialists to coordinate and apply a diverse
range of treatments to achieve a desired outcome for the patient.
In particular, the overlay or superposition of a variety of image
information, including 2D X-Ray, 3D teeth image data, photographic
data, CT scan data, and other data, and the ability to toggle back
and forth between these views and simulate changes in position or
shape of craniofacial structures, and the ability to share this
virtual patient model across existing computer networks to other
specialists and device manufacturers, allows the entire treatment
of the patient to be simulated and modeled in a computer.
Furthermore, the expected results can be displayed before hand to
the patient and changes made depending on the patient input.
[0049] With the above general description in mind, additional
details of presently preferred components and aspects of the
inventive system and the software modules providing the functions
referenced above will be described next.
[0050] Bracket-Slot-to-Wire Play Compensation
[0051] For orthodontic treatment of a patient, orthodontic
archwires are used to apply forces to brackets bonded onto the
patient's teeth to move the teeth into the desired positions for
achieving the target of the treatment. The archwire is inserted
into the bracket slots; therefore it is of a smaller cross-section
than the bracket slots.
[0052] During the treatment planning process, customized archwires
are designed based upon the individual treatment goals (target
positions of teeth) and individual bracket positions on the teeth
to increase the effectiveness of the archwires in achieving the
treatment goals. Customized archwires comprise alternating sliding
segments interconnected by segments with bends and/or twists in
three-dimensional space. Sliding segments may comprise either
straight or smoothly curved segments or a combination thereof. The
sliding segments are placed in the bracket slots and exert forces
on the brackets for moving the teeth towards the target positions.
However, the effectiveness of a customized archwire can be reduced
when one or more archwire segments fail to engage the bracket slots
properly due to the extra space surrounding the archwire segments
occupying the bracket slots, since the archwires cross-sections, as
discussed above, are smaller in dimensions then the bracket slots
they occupy. The space between a bracket slot and a sliding segment
of the archwire occupying the bracket slot is hereinafter referred
to as bracket-slot-to-wire play. The preferred embodiment of the
invention disclosed herein teaches methods for offsetting the
undesired effects of the bracket-slot-to-wire play by properly
engaging the archwire in the bracket slots. The scope of the
customized archwire design is expanded to include positioning the
geometry of the archwire sliding segments in relation to the
bracket slots in order to properly compensate for the
bracket-slot-to-wire play.
[0053] FIGS. 2A and 2B illustrate in detail the concept of the
bracket-slot-to-wire play.
[0054] FIG. 2A shows the front-view of an example bracket 110 with
slot 112 having the width 114. An example archwire sliding segment
120 having width 122 is inserted in the slot 112 of bracket 110.
The archwire sliding segment 120 has x-axis 124, y-axis 126 and
z-axis 128 with x-axis, y-axis and z-axis crossing at the center
130. Axes x, y and z are orthogonal to each other. The
bracket-slot-to-wire play 140 in this case is the space between the
bracket slot 112 and the archwire sliding segment 120.
[0055] FIG. 2B shows a cross-sectional view 160 of the bracket 110
and the cross-sectional view 170 of the archwire sliding segment
120, both shown in FIG. 2A, taken at the z-axis plane in FIG. 2A
and viewed from the direction A. The sliding segment is generally
straight, however, one skilled in the art would appreciate the
sliding segment having a smoothly curved shape. The bracket slot
cross-section 162 has the width 114 the same as in FIG. 2A. The
archwire cross-section 170 has the width 122 the same as in FIG.
2A, and the height 172. For the archwire cross-section 170, the
y-axis 126 and the z-axis 128 and the center 130 remain the same as
in FIG. 2A. The bracket-slot-to-wire play 180 is the space
surrounding the archwire cross-section 170 bounded by the bracket
slot cross-section 162. Although the archwire cross-section 170
shown in FIG. 2B is rectangular in shape with sharp or unrounded
edges, one skilled in the art would appreciate that the archwires
with cross-sections having variety of geometrical shapes, such as
for example, square with sharp edges, rectangular with rounded
edges, square with rounded edges, elliptical, round, etc. are
possible.
[0056] As a typical deficiency, the bracket-slot-to-wire play
prevents an archwire from exerting the desired torque to move a
tooth in the facial or lingual direction. According to the
preferred embodiment of the invention, this deficiency can be
offset by properly rotating (or twisting) the sliding segment of
the archwire along the long axis of the wire or x-axis. FIG. 3
shows an enlarged view of the cross-section of the bracket 210
which is similar to the bracket cross section 160 in FIG. 2B. In
order to achieve the desired torque the sliding segment of the
archwire going through the bracket slot 212 is rotated such that
its cross-section 220 engages the walls of the bracket slot at
points 230 and 232, and optionally at point 234 as well. In order
to explain the nature of rotation a reference to FIGS. 2A and 2B
will now be made. Imagine that in FIG. 2A, the archwire sliding
segment 120 is rotated or twisted uniformly between the end points
P1 and P2 of the archwire sliding segment 120 along the x-axis 124
until the diagonally opposite corner-points of the archwire
cross-section 170 of FIG. 2B touch the walls of the bracket slot
162 in FIG. 2B. The same type of rotation as described above is
made of the archwire having the cross-section 220 and around the
center point 228 in FIG. 3. The direction of rotation 240 of the
archwire causes the archwire cross-section 220 rotated by degrees
identified by the angle 250. The y-axis 224 and the z-axis 226
moved as a result of the rotation in the positions shown in FIG. 3.
One skilled in the art would appreciate that if the desired torque
is facial torque than the rotation of the archwire would be in the
facial direction; whereas if the desired torque is lingual, then
the rotation of the archwire would be in the lingual direction,
opposite to the direction for the facial torque.
[0057] The amount of the bracket-slot-to-wire play is determined by
the size of the bracket slot and the size of the archwire in terms
of its cross section. The bracket slots are specified in terms of
the width dimension with a tolerance; and the archwires are
specified in terms of the cross-section and tolerances. One can use
the data supplied by the manufacturers of the brackets and the
archwires to compute the size of the bracket-slot-to-wire play.
Alternately, one can scan the bracket and the archwire of interest
to determine the actual size of the bracket slot and the archwire
cross-section in order to determine the actual value of the
bracket-slot-to-wire play. FIG. 4A shows an example bracket-slot
with industry standard specification of width equal to 0.46 mm+0.04
mm tolerance; and an example archwire with cross-section of 0.41
mm-0.01 mm tolerance.times.0.56 mm-0.01 mm tolerance; and rounded
edges with a small radius. The archwire has rectangular
cross-section with sharp un-rounded edges (or edges rounded with a
very small radius not shown in this figure). The degree of rotation
of the sliding segment of the archwire that can be realized in this
case is 5.7.sup.0. FIG. 4B shows the same bracket slot and the
archwire combination as in FIG. 4A, with the exception that the
archwire cross-section has rounded edges with a larger radius. The
resulting degree of rotation of the sliding segment of the archwire
that can be realized is 28.6.sup.0. One skilled in the art would
appreciate the calculation of the bracket-slot-to-wire play
required for a smoothly curved segment can be done at the first
contact point of the wire and the bracket slot. In the symmetric
case, this can be done at the midpoint of the sliding segment.
[0058] FIG. 5 shows an example where the tooth 302 requires facial
torque and an additional slot-filling torque 304 in the amount of
5.sup.0, which has been automatically calculated by the treatment
planning software to fully engage the bracket slot. FIG. 5 also
shows the slot 310 for the bracket associated with tooth 302 and
the archwire cross-section 320 rotated in the facial direction to
fully engage the bracket.
[0059] FIG. 6 shows the same example tooth 302 as in FIG. 5.
However, if the practitioner desires lingual tooth movement, the
automatic determination by the treatment planning software changes
the additional slot-filling torque 304' to a lingual torque in the
amount of -5.sup.0. FIG. 6 shows the same slot 310 for the bracket
as in FIG. 5 associated with tooth 302. However, the archwire
cross-section 320' is now rotated in the lingual direction to fully
engage the bracket.
[0060] FIG. 7 shows the same example tooth 302 as in FIG. 5. Tooth
302 is shown in two different positions, namely the tooth 302 in
the target position 302'' superimposed over the tooth 302 in the
initial position 302'. The bracket with the slot 310 is shown
bonded to the target position 302''. The archwire cross-section 320
is shown in the rotated position just the same as in FIG. 5 for
delivering the facial torque with the additional slot-filling
torque 304 in the amount of 5.sup.0. The tooth 302 in the target
position 302'' superimposed over the tooth 302 in the initial
position 302' is shown in the form of a cross-section made possible
by the clipping plane tool in the treatment planning software.
[0061] As another deficiency, the bracket-slot-to-wire play
prevents an archwire from exerting the desired angulation force to
move a tooth in the mesial or distal direction. According to
another preferred embodiment of the invention, this deficiency can
be offset by properly rotating the sliding segment of the archwire
around the y-axis of the wire. FIG. 8A shows that a tooth 402
labeled as 1 requires an additional slot-filling mesial angulation
404 of 1.sup.0. Bracket 410 is associated with tooth 402. The
bracket slot 412 is engaged by straight archwire segment 420. The
straight archwire segment 420 has x-axis 422, y-axis 424, z-axis
426 and the center 428. In order to provide the desired mesial
angulation, the straight archwire segment 420 is rotated around the
center 428 in the rotation direction 440 such that the straight
archwire segment 420 makes surface contact with the walls of the
bracket slot 412 at locations 450 and 452.
[0062] FIG. 8B is very similar to FIG. 8A, except that the tooth
402 labeled as 1 in this case requires an additional slot-filling
distal angulation 404' of -1.sup.0. Bracket 410 remains associated
with tooth 402. The bracket slot 412 is engaged by straight
archwire segment 420. The straight archwire segment 420 has x-axis
422, y-axis 424, z-axis 426 and the center 428. In order to provide
the desired mesial angulation, the straight archwire segment 420 is
rotated around the center 428 in the rotation direction 440' such
that the straight archwire segment 420 makes surface contact with
the walls of the bracket slot 412 at locations 450' and 452'.
[0063] As yet another deficiency, the bracket-slot-to-wire play
prevents an archwire from exerting the desired force to rotate a
tooth in the mesial or distal direction. According to yet another
preferred embodiment of the invention, this deficiency can be
offset by properly rotating the sliding segment of the archwire
around z-axis. In order to explain this embodiment of the
invention, reference is made back to FIG. 2A. The archwire sliding
segment 120 is rotated around the z-axis 128 either in the mesial
direction if the mesial rotation is desired, or in the distal
direction if the distal rotation is desired, until the archwire
comes in firm contact with the bottom wall of the bracket-slot
occupied by the archwire.
[0064] As yet another deficiency, the bracket-slot-to-wire play
prevents an archwire from exerting the desired translational force
to move a tooth in the buccal or lingual direction. According to
yet another preferred embodiment of the invention, this deficiency
can be offset by properly moving the sliding segment of the
archwire along y-axis. In order to explain this embodiment of the
invention, reference is made again back to FIG. 2A. The archwire
sliding segment 120 is moved along y-axis 126 either in the buccal
direction if the buccal translation is desired, or in the lingual
direction if the lingual translation is desired. O-rings or
wire-ties are placed on the bracket in order to keep the archwire
within the bracket slot and can be used to achieve the buccal
movement. On the other hand when the translational movement of the
archwire segment in the lingual direction is required then the
archwire is moved in the lingual direction until it comes in firm
contact with the bottom of the bracket-slot occupied by the
archwire.
[0065] As yet another deficiency, the bracket-slot-to-wire play
prevents an archwire from exerting the desired translational force
to move a tooth in the occlusal or gingival direction. According to
yet another preferred embodiment of the invention, this deficiency
can be offset by properly moving the sliding segment of the
archwire along z-axis. In order to explain this embodiment of the
invention, reference is made again back to FIG. 2A. The archwire
sliding segment 120 is moved along z-axis 128 either in the
occlusal direction if the occlusal translation is desired, or in
the gingival direction if the gingival translation is desired. When
the translational movement of the archwire segment in the occlusal
direction is required then the archwire is moved in the occlusal
direction until it comes in firm contact with the lower side wall
of the bracket-slot occupied by the archwire. On the other hand
when the translational movement of the archwire segment in the
gingival direction is required then the archwire is moved in the
gingival direction until it comes in firm contact with the upper
side wall of the bracket-slot occupied by the archwire.
[0066] In summary, the deficiencies caused by the
bracket-slot-to-wire play by disabling an archwire from exerting
the desired force in any of the 5-degrees of freedom, namely torque
(facial and lingual), angulation (mesial and distal), rotation
(mesial and distal), buccal and lingual translation and occlusal
and gingival translation, can be offset by the various embodiments
of the invention disclosed above. A user can manually or
automatically identify the type of deficiency caused by the
bracket-slot-to-wire play, given bracket slot size and the archwire
cross section parameters, and manually or automatically determine
the method of offsetting the deficiency, by using the software
tools available in the treatment planning workstation. The desired
offset for the compensation of the bracket-slot-to-wire play is
displayed on the display of the treatment planning workstation. The
user can override the offset automatically determined by the
treatment planning software and simulate and design the archwire
based upon the offset determined to be more desirable by the user
or the practitioner. If the desired tooth position cannot be
achieved with a single offset, then the practitioner may choose to
accomplish that in multiple stages of the tooth movement during the
course of the treatment by changing the design of the archwire as
the treatment progresses. Also, it is possible that multiple types
of deficiencies may be caused by the bracket-slot-to-wire play. In
that case the practitioner may choose to combine the remedies for
one or more deficiencies using the procedure described above for
each degree of freedom, i.e. torque, angulation, rotation and
buccal-lingual and occlusal-gingival translations; or approach the
remedies in treatment stages.
[0067] FIG. 9 illustrates the process of designing the desired
offset to compensate for the bracket-slot-to-wire play by way of an
example. In this figure, the user has selected tooth 502 in the
upper jaw of the patient. Digital or virtual models of the
patient's teeth in the initial positions as well as the target or
set-up positions are available. FIG. 9 shows a portion of the
selected tooth in the initial position 502 along with a portion of
the same tooth in the target or set-up position 502'. In this
example the desired tooth displacement from the initial position to
the target position requires one additional degree of distal
angulation 504 (shown as -1 in FIG. 9) to fully engage the bracket
slot. The desired displacement can be realized by adjusting the
sliding segment 520 of the archwire, which is inserted into the
slot of the bracket 510 shown bonded to the tooth in the target
position 502', using the procedure described earlier for designing
the archwire for handling angulation displacement. The new
customized design of the archwire segment to compensate for the
bracket-slot-to-wire play will be included in the prescription to
bend the archwire. One skilled in the art would appreciate that
this methodology of designing the compensation for
bracket-slot-to-wire play can be applied to plurality of teeth for
designing the customized archwire. The process can be carried out
by the practitioner in the practitioner's office, at the
`chair-side while examining the patient` if so desired, or at a
different location away from the practitioner's office using the
internet as a vehicle of communication between different
workstations.
[0068] In summary then, according to the preferred embodiment of
the invention, the procedure described below is utilized to realize
compensation for the bracket-slot-to-wire play.
[0069] 1. Quantify the bracket-slot-to-wire play. [0070] (a) This
can be accomplished if one of the following items is known. [0071]
i. ideal slot size and ideal archwire cross-section; [0072] ii.
tolerance model of slot and tolerance model of the archwire
cross-section; [0073] iii. actual (measured) model of slot and
actual (measured) model of the archwire cross-section (for each
individual item or on a lot bases); or [0074] iv. every possible
combination of the above three items. [0075] (b) It can be
determined from the actual and target positions of bracket
slots.
[0076] 2. Then the offset to compensate for the
bracket-slot-to-wire play can be determined as follows: [0077] a.
Calculate the slot play between the bracket-slot and the height of
the archwire. [0078] b. Calculate the direction of the intended
movement in coordinates of the bracket slot. (i.e., initial or
actual to target or set-up) [0079] c. Calculate the maximum
possible rotation or translation of the archwire sliding segment in
the bracket-slot, so that the sides or the edges of the archwire
touch the sides of the walls of the bracket-slot, based upon the
direction of the information from step 2.b.
[0080] The bracket-slot-to-wire play offsetting compensations are
made part of the customized archwire design and included in the
prescription for manufacturing the customized archwire.
[0081] While presently preferred embodiments of the invention have
been described for purposes of illustration of the best mode
contemplated by the inventors for practicing the invention, wide
variation from the details described herein is foreseen without
departure from the spirit and scope of the invention. This true
spirit and scope is to be determined by reference to the appended
claims. The term "bend", as used in the claims, is interpreted to
mean either a simple translation movement of the work-piece in one
direction or a twist (rotation) of the work-piece, unless the
context clearly indicates otherwise.
[0082] Compensation Archwire Design Based Upon Progress Model and
Target Set-Up
[0083] As described earlier, orthodontic arch-wires are used to
apply forces to brackets bonded to patients' teeth. The purpose of
these arch-wires is to move the teeth into desired positions to
achieve some treatment goals. By pre-planning the desired teeth
positions using a computer and CAD/CAM software, it is possible to
design and produce customized arch-wires which direct tooth
movement to pre-planned positions. The arch-wire can be designed by
determining desired tooth positions, locating the position and
orientation of brackets on each tooth and calculating the shape of
an arch-wire that would exert no force when the teeth are in their
desired final positions. Once produced and inserted into the
brackets on a patient's teeth, the arch-wire acts as a spring
forcing the teeth to move toward their intended final
positions.
[0084] However, a typical orthodontic arch-wire is not able to
accomplish all desired movements without auxiliary appliances in
all cases. For example, an arch-wire does not exert any force along
the length of the wire, so it is not possible to move teeth along
the wire without additional appliances. In this case, coil springs
or elastics are used to force the teeth to move along the wire. Nor
does a typical arch-wire exert forces between teeth in opposing
jaws. So, other types of springs or elastics are used to affect
inter-arch positioning. Additionally, individual biology can affect
the results of an arch-wire. In the majority of cases, auxiliary
appliances, such as springs or elastics are applied in conjunction
with the archwire. The combination of individual biology and the
often used auxiliary appliances results in unknown additional
forces applied to the teeth. Thus, a method is required to
determine adjusted customized arch-wires and thereby achieve the
desired treatment goals and overcome the effects of additional
force systems.
[0085] Interactive, computer-based treatment monitoring is a
significant advantage provided by the treatment planning and
appliance design aspects of the system described herein. Typically,
when the patient comes into the office during treatment, they will
be scanned and a new digital model of the dentition is acquired.
From this new model, differences between the current situation and
the original malocclusion, and differences between the current
situation and the target situation or pre-defined limits or
treatment stages as defined earlier can be determined. These
differences can be quantified with precision. For example, a point
on the tooth in the current model is selected, and the model of the
tooth at the original malocclusion is overlaid on the screen. The
superposition of the two teeth allows the user to view the change
in position that has occurred. The measurement marker features
described earlier allow the user to quantify precisely the amount
of movement.
[0086] Any deviations between the therapeutic result that is
observed and the expected result can be captured precisely and at
an early stage in treatment using the scanning and treatment
planning features described herein, and corrected for. For example,
the orthodontist may need to place additional bends in the
archwire. Such additional bends can be performed by simulating the
wire shape on the screen, displaying the wire only on the screen,
and printing out the screen and using it as a template for bending
the wire. The current situation could also be forwarded to the
precision appliance center for manufacture of a new appliance. Of
course, these monitoring and treatment corrections are applicable
to any type of appliance selected for the patient.
[0087] The adjusted customized arch-wire can be designed after an
initial customized arch-wire has been used to treat a patient and
is at or near equilibrium. The initial custom arch-wire is first
designed by producing a 3D computer-based, geometrical model of a
patient's dentition, locating brackets on the digital tooth model,
moving the digital tooth models to planned final positions and
orientations, and then calculating a wire which fits in the slots
of the brackets while the teeth are at their planned final
positions and exerts no forces on the brackets. This wire is
produced according to the design and delivered to the practitioner
who subsequently inserts the wire into the brackets in the
patient's mouth. After a period of time the teeth will move under
the force of the wire and will eventually move into positions such
that the forces from all appliances and biological systems are in
equilibrium. If the teeth are not in the final planned positions at
that point in time, the adjusted custom arch-wire is designed and
applied.
[0088] The design of the adjusted wire is accomplished first by
making a 3D computer-based geometrical model of the positions of
teeth at equilibrium. This model is referred to as a progress model
because it captures the treatment progress. This model can be
produced via scanning the tooth positions and processing the scan
data into models or by moving the tooth models interactively in a
computer-based software system to estimate the actual tooth
positions in the mouth.
[0089] Then, tooth by tooth differences in all 6 degrees of freedom
(three positional directions and three rotational directions)
between the desired final tooth positions and the progress model
tooth positions are calculated. These differences are then added to
the initial custom wire design to determine the adjusted custom
wire design. For example, if the original plan called for the
movement of a tooth by 1 mm in the anterior direction, but after
treatment with the initial custom wire, only 0.75 mm of movement
was realized. Then, a new adjusted custom arch-wire can be made by
adding an additional 0.25 mm offset in the anterior direction to
compensate for other forces acting on the tooth.
[0090] FIG. 10 shows a screen shot of an example digital or virtual
target setup model of the dentition 620 of a patient. The model
shown is for the upper jaw. This model was developed during the
treatment planning phase for the patient. This model shows the
desired final position of teeth to be realized at the end of the
treatment.
[0091] FIG. 11 shows the three-dimensional digital or virtual
progress model 640 of the current state of the dentition of the
same patient as in FIG. 10. Here also, the model shown is for the
upper jaw. Nature and amount of displacement still required for
each tooth relative to the target setup is listed in table 650. The
displacements are automatically calculated by the treatment
planning software and displayed on the display of the treatment
planning workstation. According to a preferred embodiment of the
invention, this model is arrived at by the treatment planner by
manipulating the target setup model of FIG. 10 to match either the
visually observed state of the teeth during the treatment
monitoring visit by the patient, or the recent photographs of the
dentition of the patient. Alternately, this model is obtained by
scanning the dentition of the patient during treatment monitoring.
In a preferred embodiment of the invention described herein the
scanning is done in-vivo. Alternately, an impression of the
patient's dentition may be taken; and the scanning of the
impression or the physical model developed from the impression can
be done.
[0092] FIG. 12 shows the virtual model 680 wherein the brackets 684
are attached to the teeth 682. The teeth positions shown in FIG. 12
represent the progress model shown in FIG. 10. Furthermore, nature
and amount of displacement still required for each bracket bonded
to a tooth relative to the target setup is listed in table 652.
These displacements are also automatically calculated by the
treatment planning software.
[0093] FIG. 13 shows a superimposed virtual model 660 of the
patient's dentition obtained by combining the target set-up model
620 of FIG. 10 with the progress model 640 of FIG. 11. Virtual
model 660 provides visualization of the displacements still
remaining between the actual positions of the teeth and the desired
positions of the teeth. Table 650 shows the same tooth displacement
data as in FIG. 11. The treatment planner can now automatically
design the compensation archwire by selecting `Create Compensation
Wire` tab 670 on the treatment planning workstation display shown
in FIG. 13A.
[0094] FIG. 14 shows the virtual target set-up model of the
patient's dentition previously shown in FIG. 10; and the shape of
the newly designed archwire 710 in order to compensate for
deviations between the target setup and the progress model. Also
shown in FIG. 14 is the virtual model 690 showing teeth, brackets
and the compensation archwire.
[0095] FIG. 15 shows the virtual superimposed model 660 the same as
in FIG. 13 along with the newly designed compensation archwire 710.
Also shown is a model 720 of the teeth, brackets and archwire.
[0096] FIG. 16A shows the comparison between the set-up archwire
700 and the newly designed compensation archwire 710 both shown in
the arch form.
[0097] FIG. 136B shows the same two wires as in FIG. 136A, but from
the archwire plane view perspective 700' and 710'.
[0098] In summary, often the initially designed customized archwire
for moving a patient's teeth from malocclusion to the desired
target set-up reaches an equilibrium without achieving the planned
treatment goal. In such a case the current or progress model of the
patient's teeth shows tooth displacements required to achieve the
target positions. The preferred embodiment of the invention
disclosed herein enables the practitioner evaluate the progress
model in order to determine the tooth displacements still required
to move the teeth in the desired positions; and design the
compensation archwire by making adjustments necessary to the
initial design of the arch wire. The compensations can be made to
achieve displacements in all 6 degrees of freedom, i.e. misial or
distal translational displacement, buccal or lingual translational
displacement; occlusal or gingival translational displacement,
facial or lingual torque, mesial or distal angulation and mesial or
distal rotation. The treatment planning software performs
calculations automatically to determine the extent and the nature
of displacements required from the three dimensional digital models
of progress and the target. The practitioner can look at the
displacements and if they are satisfactory, then instructs the
workstation to perform the compensation design of the archwire
automatically. The workstation provides the tools whereby the
practitioner can override one or more displacements that were
automatically calculated by the treatment planning workstation; and
specify new values for the selected displacements. Then the
compensation archwire design is performed using the displacement
parameters specified by the practitioner or the treatment planner.
The complete compensation archwire design can be carried out by the
practitioner at patient's `chair side` at the practitioner's
practice or by a treatment planner at a remote location and can be
communicated to the practitioner via internet communications. The
compensation design can be simulated by varying the displacement
parameters using the treatment planning workstation so as to
evaluate multiple options for the compensation design of the
archwire.
[0099] The process can be summarized as follows:
[0100] A method of designing the shape of a compensating
orthodontic arch-wire inserted into slots of brackets bonded to
teeth of an orthodontic patient is disclosed based upon progress
model of treatment and initial archwire design, utilizing a
workstation. The steps comprise:
[0101] a. retrieving a three-dimensional digital model of the
target positions of the teeth of an orthodontic patient;
[0102] b. retrieving initial design of the archwire customized to
move the patient's teeth from malocclusion to target set-up;
[0103] c. obtaining a three-dimensional digital model of the
current positions of the teeth of the orthodontic patient;
[0104] d. computing differences in 3 translational degrees of
freedom and 3 rotational degrees of freedom between the target
positions of teeth and the current positions of teeth per the
progress model; and
[0105] e. designing shape of the compensating orthodontic arch-wire
based upon adding said differences to the initial design of the
archwire performed to move the teeth in the initial position or
malocclusion to the target or desired final position or set-up.
[0106] The design of the initial archwire is performed as
follows:
[0107] i. obtaining a digital model of the malocclusion of the
patient's teeth;
[0108] ii. performing treatment planning simulation using the
digital model of the malocclusion; thereby obtaining a
three-dimensional digital model of target positions of the teeth
from the digital model of the malocclusion. The digital model of
malocclusion of the patient's teeth can be obtained by in-vivo
scanning said patient's dentition, or by scanning an impression of
the patient's dentition, or by scanning a physical model of the
patient's dentition. The current positions of teeth of an
orthodontic patient can be arrived at by a practitioner by
manipulating the three-dimensional digital model of the target
positions of teeth of the orthodontic patient to match with
visually observed state of teeth of the patient during a treatment
monitoring visit by the patient. Alternately, the current positions
of teeth of the orthodontic patient can be arrived at by a
practitioner by manipulating the three-dimensional digital model of
the target positions of teeth of the orthodontic patient to match
with recent photographs, which may be taken at the practitioner's
office, or are otherwise available, of the dentition of the
patient. Alternately, the current position of teeth of the
orthodontic patient is arrived at by the practitioner by in-vivo
scanning the teeth of the patient during a treatment monitoring
session; or by scanning an impression or a physical model made from
the impression of the patient's dentition. Additionally, the tooth
displacements that can be attributed to the bracket-slot-to-wire
play in the progress model can also be addressed as a part of the
compensation archwire design. As described earlier, displacements
in 5 degrees of freedom can be handled through offsetting the
bracket-slot-to-wire play by additional compensations of the
archwire design.
[0109] While presently preferred embodiments of the invention have
been described for purposes of illustration of the best mode
contemplated by the inventors for practicing the invention, wide
variation from the details described herein is foreseen without
departure from the spirit and scope of the invention. This true
spirit and scope is to be determined by reference to the appended
claims. The term "bend", as used in the claims, is interpreted to
mean either a simple translation movement of the work-piece in one
direction or a twist (rotation) of the work-piece, unless the
context clearly indicates otherwise.
* * * * *